Studies are proposed for the development of a bio-compatible approach to integration of enzymes of enzymes and electrodes by using scaffoldings of a polysaccharide biopolymer, chitosan. Such enzyme electrodes are projected to have better operational stability, insufficient biocompatibility with enzymes and limited selectivity. Chitosan has been selected because of an unusual combination of its properties which include excellent membrane forming ability, good adhesion, biocompatibility, and susceptibility to chemical modifications due to the presence of reactive hydroxyl and amino function groups. In order to take advantage of these properties, enzymes will be incorporated into thin films of chitosan cast on electrode surfaces. The work is reliant on covalent attachment of enzymes to chitosan chains by using bifunctional cross-linkers. The amino and hydroxyl groups of chitosan will also be used for attachment of redox mediators as well as permeability controlling agents in order to introduce an extra level of molecular recognition. Such hybrid materials will provide the basis for a new line of stable biosensors in which the selectivity of the enzymatic reaction will not be compromised by the signal transduction process. In the second part of the project, the protective matrix of chitosan will be combined with solid electrocatalysts based on transition metal complexes. Preliminary studies showed that such redox crystals, when assembled together with glucose oxidation in chitosan films, promote anaerobic reoxidation of the enzyme at a very low driving force. This phenomenon may represent a new mode of electron transfer that may be relevant for future biosensor development. For proof-of-concept purposes, several oxidase enzymes (glucose oxidase, L-glutamate oxidase, L-AND D-AMINO acid oxidase, L-lactate oxidase, diamine oxidase), and redox mediators (Ru and Os complexes) will be immobilized within the host matrix of chitosan deposited on the electrode surfaces. Electrochemical and spectroscopic techniques will be used to probe for the composition-stability reactivity patterns in such integrated biosensing layers. The proposed materials will be appropriate not only for sensor applications, but also for basic studies of the transfer reactions and ability to manipulate them will lead to further developments, not only in the biosensor field but also in bioelectronics. Central to this is our ability to interface the biological system and electrode in a stable fashion. This fundamental question stimulated the present proposal.